Replication RCT of early universal prevention effects on young adult substance misuse

Abstract

Objective: For many substances, more frequent and problematic use occurs in young adulthood; these types of use are predicted by the timing of initiation during adolescence. We replicated and extended an earlier study examining whether delayed substance initiation during adolescence, resulting from universal preventive interventions implemented in middle school, reduces problematic use in young adulthood.

Method: Participants were middle school students from 36 Iowa schools randomly assigned to the Strengthening Families Program: For Parents and Youth 10-14 (Molgaard, Spoth, & Redmond, 2000) plus Life Skills Training (LST; Botvin, 1995, 2000), LST-only, or a control condition. Self-report questionnaires were collected at 11 time points, including 4 during young adulthood. The intercept (average level) and rate of change (slope) in young adult frequency measures (drunkenness, alcohol-related problems, cigarettes, and illicit drugs) across ages 19-22 were modeled as outcomes influenced by growth factors describing substance initiation during adolescence. Analyses entailed testing a 2-step hierarchical latent growth curve model; models included the effects of baseline risk, intervention condition assignment, and their interaction.

Results: Analyses showed significant indirect intervention effects on the average levels of all young adult outcomes, through effects on adolescent substance initiation growth factors, along with Intervention × Risk interaction effects favoring the higher risk subsample. Additional direct effects on young adult use were observed in some cases. Relative reduction rates were larger for the higher risk subsample at age 22, ranging from 5.8% to 36.4% on outcomes showing significant intervention effects.

Conclusions: Universal preventive interventions implemented during early adolescence have the potential to decrease the rates of substance use and associated problems into young adulthood.

Figure 1

Young adult indirect intervention effects outcome model, mediated through adolescent substance initiation

Figure 2

Study participation by wave Notes: LST = Life Skills Training. SFP 10–14 + LST = Strengthening Families Program: For Parents and Youth 10–14 + Life Skills Training. Participation in the SFP 10–14 or SFP 10–14 + LST condition was 25%. Participation in a given wave of data collection was not contingent on participation in a prior wave (all enrolled students in the targeted grade were recruited for participation at each wave). The enrolled samples showed considerable stability from year to year; however, we eliminated from the sample those students who changed conditions (i.e., moved from a school district in one condition into one in a different condition) to preserve randomization (n = 18). Following high school, a selected sample was assessed, based on their participation in previous waves (i.e., those present at the pretest and the 11th and/or 12th grade data collection, plus any others who participated in in-home family assessments during adolescence; total eligible n = 1410).

Figure 2

Study participation by wave Notes: LST = Life Skills Training. SFP 10–14 + LST = Strengthening Families Program: For Parents and Youth 10–14 + Life Skills Training. Participation in the SFP 10–14 or SFP 10–14 + LST condition was 25%. Participation in a given wave of data collection was not contingent on participation in a prior wave (all enrolled students in the targeted grade were recruited for participation at each wave). The enrolled samples showed considerable stability from year to year; however, we eliminated from the sample those students who changed conditions (i.e., moved from a school district in one condition into one in a different condition) to preserve randomization (n = 18). Following high school, a selected sample was assessed, based on their participation in previous waves (i.e., those present at the pretest and the 11th and/or 12th grade data collection, plus any others who participated in in-home family assessments during adolescence; total eligible n = 1410).

Figure 3

Adolescent substance initiation by condition and risk

Figure 4

Young adult substance misuse outcomes by condition and risk: (a) Drunkenness, (b) Alcohol-Related Problems, (c) Cigarette Use, (d) Illicit Drug Use

Figure 4

Young adult substance misuse outcomes by condition and risk: (a) Drunkenness, (b) Alcohol-Related Problems, (c) Cigarette Use, (d) Illicit Drug Use